24 
C. A. LUDWIG 
exposed to ethylene was good in all cases tested. In 50 percent of 
the gas it was quite equal to the air culture and in 85 percent it was 
only slightly less vigorous. 
Bacillus melonis. — In one trial the growth of B. melonis in both 
ethylene contents was about equal to that in air. In the other there 
was slight inhibition in the 85 percent concentration. 
Bacillus campestris. — The tests seemed to show a slight inhibition 
of B. campestris at 50 percent of ethylene although they did not agree 
especially well on the point. At 85 percent the inhibition was some- 
what greater but not at all remarkable. 
Bacterium tumefaciens. — With B. tumefaciens the tests showed a 
clear inhibitive effect at both concentrations of the gas but greater 
at 85 percent than at 50 percent, and the effect was maintained until 
the cultures were removed to the air. 
Bacillus solanisaprus . — The growth of B. solanisaprus in the two 
ethylene-air mixtures was practically equal to that of the same 
organism in air. 
Bacillus radicicola. — The development of the check culture of B, 
radicicola in air and of the cultures in 50 percent and 85 percent 
ethylene were practically identical in both tests. 
Bacillus mycoides. — In the first test with B. mycoides, where the 
inoculation was made in a streak, no difference could be made out 
between the growth in air and in the ethylene. In the second test, 
however, where the slant was inoculated at a single spot near the 
center, it took about four days for the colony to spread over the entire 
slant in 85 percent ethylene, and about three days in 50 percent 
ethylene, while in air the invasion was complete in two days. 
It seems quite clear to the writer from the results mentioned above 
that the presence of 4-5 percent of ethylene in illuminating gas is 
totally inadequate to account for its effect on the bacteria and fungi 
studied. 
4. Carbon Monoxide 
Production and Purification of the Gas 
The carbon monoxide used in these studies was made by heating 
crystallized potassium ferrocyanide with c.p. sulphuric acid and a 
little water. It was bubbled through sodium hydroxide solution to 
remove the small amounts of CO2 and SO2. In the earlier work it 
